CALOTRICHES. 279 
of the two plants at other periods of the season. Other two lochs in the 
vicinity did not contain the plants alluded to.” 
As these pages are being printed (July, 1884,) this alga has been sent 
us from a large pond between Haslemere and Farnbam, rendering the 
water quite opaque, described as “like a mixture of pea soup and 
water.” See also Bornet and Flahault, ‘‘Sur da determination des 
Rivulaires, &c.,” in “Bulletin de la Societe Botanique de France,” 
t. xxxi., p. 76 (1884). 
Plate CXIV. fig. 2. a, natural size ; b, cluster magnified ; ¢, trichomes 
X 400 diam. 
Rivularia calcarea. ng. Bot. 11. ed., t. 1799. 
Hemispherical, gregarious, confluent in a very hard mamil- 
lose incrusting blue-green or brownish stratum, internally re- 
peatedly zoned, zones of a darker green, trichomes rather thick, 
pale blue green, slightly flexuous, distinctly articulate, ending 
at the apex in a colourless hyaline point; sheaths narrow, 
colourless or brownish at the base; heterocysts globose, lower 
joints of the trichomes equal in length to their diameter. 
Sizz. Trichomes :006 mm. diam. 
Eng. Fl. v., 892. Harv. Man. 150. 
Ainactis calcarea, Kutz. Tab, Phye. ii, t. 63, f. 11. 
Lithonema calcarea, Hass. Alg. 265, t. 65, f. 2. 
Zonotrichia calcarea, Rabh. Alg. Eur. ii., 213. 
Linckia dura, a calcarea, Grev. Fl. Edin. 322. 
On rocks and stones in streams. 
Plate CXVI. fig. 3. u, section natural size ; 6, portion with trichomes 
X 400 diam. 
Rivularia dura. Kutz. 
About the size of a mustard seed, rather hard, dark bluish- 
green, becoming brownish or brackish; trichomes eruginous, 
variable in the same thallus, some thin and inarticulate, others 
thicker, articulate and torulose, all with distinct sheaths, 
lengthened at the apex into a colourless flexuous inarticulated 
thread ; lower joints as long as broad, or nearly so, upper ones 
longer, all granulated; sheath colourless, or yellowish ; hetero- 
cysts rounded, oblong. 
Sizz. Trichomes ‘008-009 mm. diam. at the base. 
Limnactis dura, Kutz, Tab. Phyc. ii, t. 64, f. 1. Rabh. Alg. 
Eur. ii., 211. 
Rivularia radians, var. dura, Kirch, Alg. Schles. p. 223. 
Attached to aquatic plants, especially Chara. 
Plate OXY. fig. 2. a, natural size, 6, section enlarged; ¢, trichomes 
x 400 diam. 
